$s = 123;
$s = 456;
print "$s\n";  # 456

$a[1] = 123;
$a[1] = 456;
print "$a[1]\n";  # 456

$h{foo} = 123;
$h{foo} = 456;
print "$h{foo}\n";  # 456

##</code><code>##

push @{ $h{$k} }, 123;
push @{ $h{$k} }, 456;
print "$_\n" for @{ $h{$k} };  # 123, 456